This invention relates to components for high-temperature secondary electrochemical cells including the positive and negative electrodes and separators therefor. Batteries of such electrochemical cells are contemplated for use as power sources for electric automobiles, storage of electric energy generated during intervals of off-peak power consumption and various other applications. The battery components of this invention are particularly applicable to electrochemical cells operated at high temperatures and therefore require the use of high-temperature insulators and electrodes.
A substantial amount of work has been done in the development of these types of electrochemical cells and their electrodes. Examples of such high-temperature cells and their various components are disclosed in U.S. Pat. No. 3,666,560 issued May 30, 1972 to Cairns et al. for Electrochemical Power-Producing Cell; U.S. Pat. No. 3,915,742 issued Oct. 28, 1975 to Battles and Mrazek for Interelectrode Separator For Electrochemical Cell; U.S. Pat. No. 3,947,291 issued Mar. 30, 1976 to Yao and Walsh entitled Electrochemical Cell Assembled In Discharged State; U.S. Pat. No. 3,992,222 issued Nov. 16, 1976 to Walsh et al. for Metallic Sulfide Additives For Positive Electrode Material Within A Secondary Electrochemical Cell; U.S. Pat. No. 4,086,396 issued Apr. 25, 1978 to Mathers et al. For Electrochemical Cell With Powder Electrically Insulative Material As A Separator; U.S. Pat. No. 4,011,374 issued Mar. 8, 1977 to Kaun for Porous Carbonaceous Electrode Structure And Method For Secondary Electrochemical Cell; and U.S. Pat. No. 4,087,905 issued May 9, 1978 to Cooper et al. for Method Of Preparing A Powdered Electrically Insulated Separator For Use In An Electrochemical Cell.
Previous electrochemical cells which operate at high temperatures in the range of between about 300.degree. C. to about 600.degree. C., have required the use of suitable high-temperature materials. For these electrochemical cells, refractory, electrically insulative material such as boron nitride and yttrium oxide have been fabricated into cloth, netting, felt, paper, and other fabrics to provide suitable interelectrode separators. Although these efforts have been successful to some extent, they involve difficult and expensive fabrications which are high labor-intensive processes. In addition, sometimes the separator components thus provided are not sufficiently tough and durable. Other oxides and nitrides of metals and metaloids such as magnesium oxide, calcium oxide, silicone nitride and aluminum nitride are available for use in powder form as taught by the Mathers et al. and Cooper et al. patents.
Both the Mathers et al. and Cooper et al. patents disclose the use of powdered ceramics but neither discriminates between ceramics which are sulfide compatible and ceramics which are not sulfide compatible; neither discriminates between undesirable ceramics which are soluble in the contemplated electrolytes and ceramics which are substantially insoluble in the electrolyte and are therefore desirable. Both the Mathers et al. and Cooper et al. patents disclose processes which are highly labor intensive and require substantial amounts of time to fabricate the separators disclosed therein, whereby neither of these patents teaches a method which is adaptable to high speed commercial production of components for the contemplated high-temperature electrochemical cells.